In order to stabilize and support underground excavations, such as mine stopes, drifts, galleries, etc., grouted rock and cable bolts are oftentimes utilized. Grout is prepared, mixed and pumped into the bore hole where it sets about the bolt.
There are a number of grout pumps presently available. However, they generally are limited to pumping low density cementitious grouts. That is, grouts having a 0.4/1.0 water/cement ratio (by weight) or higher i.e., 0.5/1.0 water/cement ratio. Thinner grouts mean less bonding strengths and lower efficiency in support systems. Moreover, due to the very nature of the grout, pumps are prone to frequent stoppages due to blockage and plugging.
Higher density grout i.e., 0.3:1 water/cement, which is more desirable, does not flow well with current pump designs. In order to cause high density grout to flow, the grout must be subject to a shear mix action. For the purposes of this specification, shear mix means that each cement particle is fully coated with water. Conventional mining grout pumps that are able to pump high density grouts cannot shear mix the high density grout.
Other pumps, if they pump a shear mix, cannot pump high density grout. An available shear mix system includes mixing blades that must rotate at 1750 revolutions per minute. These high speed systems are not practical for mining applications. Other designs employ piston type pumps which create surges that will not pass through long, small openings, i.e.--pipe bolts.
It is apparent that a grout pump is needed to easily and consistently pump a high density water/cement grout over long distances and at acceptable flow rates for bolting purposes.